1. Field of the Invention
The present invention relates to a keyboard structure of an electronic keyboard instrument, which is provided with keys whose main bodies are connected via thin plate-like hinges to base ends of these keys for pivotal motion about the base ends as key fulcrums in a key depression/release direction.
2. Description of the Related Art
A keyboard structure of an electronic keyboard instrument has conventionally been known, in which key main bodies are supported for pivotal motion via thin plate-like hinges by base ends at the rear of keys (Japanese Patent Publication No. 2628656). In the keyboard structure of this type, the hinges are horizontally rearwardly extended in substantially parallel to key depression surfaces of the keys, and thus the keys are long in longitudinal dimension. As a result, the keyboard instrument and its instrument body are long in depth.
On the other hand, Japanese Laid-open Patent Publication No. 2001-215968 discloses a keyboard structure in which hinges and base ends are extended perpendicularly downward from the rear of key main bodies, whereby the longitudinal dimension of keys is shortened.
However, in the keyboard structure disclosed in Japanese Laid-open Patent Publication No. 2001-215968, the hinges are extended parallel to the vertical direction and adapted to be deformed in the front-to-rear direction. When a force from front to rear is applied to any of the key main bodies, a corresponding hinge receives substantially the entirety of the force, and the hinge is deformed rearward. Such a force from front to rear can be generated when a key front end is simply depressed with a finger. In some cases, the key depressing force can be strong. Therefore, there is a fear that a hinge can be plastic-deformed due to an excessive force being applied thereto carelessly.
In a case where hinges are designed to be adequately long in length, the hinges are hardly plastic-deformed when applied with a force from front to rear. When the hinges are made excessively long, however, the key main bodies are likely to make rolling motion. In that case, the performance of keys are remarkably deteriorated, which is disadvantageous.